In my limited experience, squishy is good. The first female I ever tried to breed slugged out on me because I had NO CLUE what I was doing. She felt like a normal boa - hard and muscular, just a little bigger. She ate a lot of the slugs by the way, I caught her in the act.
All 4 other litters I've produced have had viable babies and each time the female felt "squishy" when held (I only hold them to transport them from cage to tub while cleaning). So, you may be right. I hope not though.
I think everyone has different practices regarding feeding and breeding. I'm a year-round kind of guy and I even feed when cooling, breeding and during gestation. In fact, I feed after the swelling from ovulation has gone down and before they even turn blue.
Thought I'd detail out my regimen. Not because I think mine is better than yours, you've CLEARLY had more success than me. In fact, some of what you do is EXACTLY in line with my practices. But this is for the benefit of those who may be interested in reading about another way to do it. I don't think either is wrong, or either is right. It's just the way we do it 
My feeding regimen is formulated around avoiding excess fat at all costs. Wild boas are never fat, so neither are my captive boas. So, there's never a "pump 'em up" season.
I feed fairly consistently all year long after I raise my temps back up to normal (ALL animals get cycled, even babies). So, once my thermostat reaches 88 degrees (goes higher - to 93 which gives a hotspot of 91), I feed a meal equal to the girth of the animal about every 14-21 days. Occasionally it's 10-14 days if I get around to it earlier. 13-17 is the norm.
Around September, I throw in about 3-4 extra meals spread over the course of 3 months (Sept 1 - Nov 30). So when they would normally get 6-7 meals in 90 days, they instead get about 10. But the meals are one step down in size (large rat eaters now get mediums) so I'm still not even "pumping 'em up". Then when I start cooling (sometime in December), I start backing off on the frequency of the meals to about 14-20 days again - but I keep the meals one step down to accommodate the cooler temps and thus, slower digestion. When I get down to daytime highs around 83-84 degrees, I step down the size of the meal again. I stop feeding below 80 degree daytime highs (which only lasts a couple of weeks). Since they're ectothermic, a lower temp means a lower metabolism and lower need for food. They always get just what they need to stay muscular, and not fat.
During courtship, I ONLY feed when the male seems to be taking a break. I'll separate them and toss a small meal to both, let them digest for 3-4 days and put them back together. By small, I mean that an "XL" eater gets a small.
After ovulation, males return to a normal feeding schedule and temperatures and the females go on a "small meal every 10 days" diet. I follow that diet for females until they're about 50 days from parturition. Then they don't eat again until they deliver. After parturition, I will feed females heavier than ever for about 3-4 meals. I give them a one-step down meal about every 8-10 days 3-4 times and then they join the rest of the group. They stay "thinner" for a while and would CERTAINLY gorge themselves if I let them, but I think fast weight gain is just fat and like I said, I avoid fat boas at all costs.
I sincerely hope your girl surprises you. It'd be great to see another Guyana litter hit the ground!
jb
-----
What's written above is purely my opinion. In fact, MOST of what you read on the internet is someone's opinion. Don't take it too seriously
Jonathan Brady
DeviantConstrictors.com
Deviant Constrictors picturetrail
